<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div{
            color: red;
        }
        .classA {
            color: blue;
        }
        #idA {
            color: black;
        }
    </style>
</head>
<body>
<div id="idA" class="classA" style="color: yellow">你好，WEB</div>
</body>
</html>